1. Field of the Invention
The present invention relates to a frequency transceiver for use in a communication system and a radar for transmitting/receiving an electromagnetic wave, and more particularly, to a frequency transceiver for automatically controlling a receive intermediate frequency (RX IF).
2. Description of the Related Art
A magnetron is a device that generates a super high frequency by using a high voltage applied from an exterior. In general, the magnetron is classified into a magnetron that generates a 2450-MHz high frequency used in a medical treatment, a microwave oven or other heaters and a magnetron that generates a 915-MHz high frequency used in an industrial heater and a continuous wave radar.
In such a magnetron, a cylindrical anode body is formed of a copper pipe or the like and a cavity resonator is disposed to maintain a radio frequency (RF) component within the cylindrical anode body. An anode section is formed by a plurality (generally, even number) of vanes arranged radially at regular intervals. A filament is arranged along a central axis of the anode body to form an activating space between the vanes and emits thermoelectrons. A pair of permanent magnets are arranged at external upper and lower sides of the activating space, with the activating space being interposed, and forms a magnetic field.
An upper shield hat and a lower shield hat are respectively arranged at upper and lower ends of the filament so as to shield the activating space. A center lead is extended along a central axis of the filament at a central region of the upper shield hat and passes through the lower shield hat, such that the center lead is extended to an outside of the activating space. A side lead is connected to the lower shield hat.
Meanwhile, if an external power is supplied, the filament is heated and thus thermoelectrons are emitted from the heated filament. The emitted thermoelectrons turn toward the vanes. At this point, since DC magnetic field intensities are different and/or the activating space is not perfectly vacuumized, a gas remaining in the activating space collides with the thermoelectrons emitted from the filament, thus generating a vibration and a noise.
In order to suppress the noise, a filter is connected to the center lead and the side lead. The filter is configured with a high-voltage cylindrical condenser and first and second choke coils. The high-voltage cylindrical condenser is connected to an external power terminal. The first choke coil has one end connected to the center lead and the other end connected to the cylindrical condenser, and the second choke coil has one end connected to the side lead and the other end connected to the cylindrical condenser.
The above-described magnetron is widely used as an RF oscillator in the radar and the like. However, the characteristics of the magnetron, such as an oscillation frequency of an RF signal, may be changed due to temperature, humidity and/or heat.
In various communication systems, such as a radar using an RF signal, a transmit/receive (TX/RX) RF signal may also be changed due to a surrounding environment. Therefore, a frequency of an RX IF signal generated from the changed RF signal is also changed and thus the RX IF signal cannot be constantly detected.